1. Field of the Invention
The present invention relates to a device for inputting coordinate information into an electronic apparatus, and more particularly, to a pressing direction sensor that can detect pressing directions and pressing forces of a finger pointing on an operation unit.
2. Description of the Related Art
Devices for inputting coordinate information into electronic devices include pointing devices. Pointing devices have been widely used as coordinate input means in personal computers and game machines. In recent years, these pointing devices are sometimes seen on small-size apparatuses such as portable telephones and PDAs, and are therefore expected to become smaller, thinner, lighter, and less costly.
For portable telephones and PDAs, onscreen pointing systems used to be required to function only from side to side and up and down. However, as the amount of information to be handled on screen has increased, cursor operations that have been employed in personal computers are expected also in portable telephones and PDAs, so that pointing operations in any direction can be performed at a controllable speed.
Various types of coordinate input mechanisms have been developed as conventional pointing devices. Those coordinate input mechanisms include: a mechanism that employs a magnet to be inclined by finger pointing and a plurality of electromagnetic conversion devices; and a mechanism that employs an optical detection system. However, any of those types of mechanisms structurally requires a certain thickness, and of course has limitations on portable devices to which it can be mounted. There are flat input devices such as touch pads, but a flat input device requires a certain area because of the operation method of stroking the pad surface with a finger.
In general, pointing devices that employ resistive film patterns and conductive pressure-sensitive rubber can achieve decreases in size and thickness. Such pointing devices have been developed and disclosed in Japanese Unexamined Patent Publication Nos. 6-139880, 7-320597, 11-203036, 2001-210191, and 2001-311671.